Various medical devices have been developed to receive information from one or more physiologic sensors or transducers. A typical physiologic sensor converts a measurable parameter of the human body, such as blood pressure, temperature or oxygen saturation for example, into corresponding electrical signals. A conventional approach to attaching a physiologic sensor to a multiple conductor lead extending from an implantable medical device involves connecting the sensor to at least two conductors provided in the lead.
Connecting two physiologic sensors to an implantable medical device in a conventional manner typically involves connecting the medical device to two multiple conductor leads, with a dedicated lead connected to each of the two sensors. The additional number of leads and associated connection hardware generally complicates the design of the leads and medical device electronics, increases power consumption and the cost of the device, and reduces overall device reliability.
An improved approach to connecting a medical device to two or more physiologic sensors is disclosed in U.S. Pat. No. 5,593,430 issued to Renger. The disclosed approach involves connecting each of the sensors in parallel to a two conductor lead. Although the number of conductor leads may be minimized to two conductors for a multiple sensor implementation, the approach disclosed in U.S. Pat. No. 5,593,430 requires deployment of a relatively complex bus protocol, such as one requiring time division multiplexing, frequency division multiplexing, or a sensor addressing scheme for coordinating bus arbitration.
Moreover, the approach disclosed in U.S. Pat. No. 5,593,430 also requires that power be applied to all sensors concurrently or removed from all sensors concurrently, even though only one of the sensors need be active or inactive during a given period of time. Assuming, arguendo, that a microprocessor bus control system, such as that disclosed in U.S. Pat. No. 5,593,430, could be used to deactivate a selected physiologic sensor, such an approach would require continuous power consumption at the sensor in order to monitor the bus for control signals transmitted by the implantable medical device. The amount of current expended by the sensor to monitor the bus would typically be on the order of a few microamps, thereby doubling the average power consumption to operate the sensor in a typical application.
Various implementations of systems for interconnecting one or more physiologic sensors with an implantable medical device are known in the art, a some examples of which may be found in the issued U.S. patents listed in Table 1 below.
TABLE 1 ______________________________________ Patent No. Inventor(s) Issue Date ______________________________________ 4,432,372 Monroe February 21, 1984 4,750,495 Moore et al. June 14, 1988 4,903,701 Moore et al. February 27, 1990 5,113,868 Wise et al. May 19, 1992 5,324,326 Lubin June 28, 1994 5,377,524 Wise et al. January 3, 1995 5,535,752 Halpenn et al. July 16, 1996 5,564,434 Halpenn et al. October 15, 1996 5,593,430 Renger January 14, 1997 ______________________________________
All patents listed in Table 1 hereinabove are hereby incorporated by reference herein in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, the Detailed Description of the Various Embodiments, and the claims set forth below, many of the devices and methods disclosed in the patents of Table 1 may be modified advantageously by using the teachings of the present invention.